From the past, work pallets (target objects) of various types for fixing a workpiece to be supplied to machining process, and work pallet positioning/fixing devices that position and fix such a work pallet on a base member, have been widely employed in practice.
For example, in the object positioning/fixing device described in Patent Document #1, a reference seating surface for positioning in the vertical direction is formed on the upper surface of a base member, and first and second reference members for positioning in the horizontal direction are provided at locations near a pair of corner portions of the base member which are in a diagonal relationship. Each of the first and second reference members comprises a flange portion that is contained in a fitting aperture in the base member and is fixed therein by a plurality of bolts, a convex engagement portion that projects upward from the central portion of this flange portion, a tapered engagement surface that is formed on the outer circumferential surface of this convex engagement portion, and a bolt hole that is formed in this convex engagement portion.
It should be understood that, while the tapered engagement surface of the first reference member is formed over the entire circumference of the outer surface portion of its convex engagement portion, the tapered engagement surface of the second reference member is formed at two locations on the outer surface portion of its convex engagement portion that oppose one another in the direction orthogonal to the line of centers that connects the axis of the first reference member and the axis of the second reference member, and a pair of shallow circular arcuate grooves are formed at the outer surface portions between this pair of tapered engagement surfaces.
Fitting apertures that are concave downward, bolt passage holes that connect to these fitting apertures, and head portion reception holes at the upper portions of these bolt passage holes for containing bolt head portions, are formed on the work pallet at positions that correspond to the first and second reference members. And first and second annular engagement members that can engage in a closely contacting state with the convex engagement portions of the first and second reference members respectively are fixed in the abovementioned fitting apertures.
With this object positioning/fixing device, by mounting the work pallet on the base member, and by passing bolts from above through the pair of bolt passage holes and screwingly engaging them into the bolt holes of the first and second reference members, it is arranged to position the pair of portions of the work pallet that neighbor its pair of corner portions on the base member in the vertical direction and in the horizontal direction and to fix them there, in the state in which the lower surface of the work pallet is seated on the reference seating surface.
Furthermore, by forming bolt holes at the other pair of corner portions of the base member that are in a diagonal relationship than the abovementioned pair of corner portions, by forming a pair of bolt passage holes in the work pallet corresponding to the pair of bolt holes, and by passing a pair of bolts from above through the pair of bolt passage holes and screwingly engaging them into corresponding bolt holes, the portions of the work pallet neighboring the other pair of corner portions are fixed to the base member.
Patent Document #1: Japanese Laid Open Pat. Publication 2011-251376